🕹️ Try the demo

jupyterlite-pyodide-lock#

Build reproducible Jupyter Lite sites with jupyterlite-pyodide-kernel and pyodide-lock.

docs	install	build

View the full documentation on ReadTheDocs.

Overview#

jupyterlite-pyodide-lock avoids run time pyodide and jupyterlite package management ambiguity by using a full web browser at build time to customize a pyodide-lock.json.

Examples#

Use jupyterlite-pyodide-lock to minimally provide a more controlled baseline pyodide runtime environment, or ensure complex dependencies like widgets are consistent over time.

Minimal Example#

Ensure pyodide-kernel's dependencies are locked, assuming pip and firefox.

Create the Minimal Build Environment#

make a requirements.txt

jupyterlite-core ==0.5.1
jupyterlite-pyodide-kernel ==0.5.2
jupyterlite-pyodide-lock ==0.1.2

Run:
```
pip install -r requirements.txt
```

Configure the Minimal Site#

build a jupyter_lite_config.json:

{
  "PyodideLockAddon": {
    "enabled": true
  }
}

Build the Minimal Site#

build a jupyter_lite_config.json:
```
jupyter lite build
```

Check the Minimal Site Works#

start a simple, local development server

cd _output
python -m http.server -b 127.0.0.1

visit the site at http://127.0.0.1:8000/
make a new Notebook
- use basic python features

Widgets Example#

Build a JupyterLite site with all the packages needed to run ipywidgets in a Notebook, assuming mamba.

Create the Widget Build Environment#

make an environment.yml

channels:
  - conda-forge
  - nodefaults
dependencies:
  - ipywidgets ==8.1.5
  - jupyterlite-core ==0.5.1
  - jupyterlite-pyodide-kernel ==0.5.2
  - jupyterlite-pyodide-lock-recommended ==0.1.2

the -recommended package includes firefox and geckodriver
optionally use a tool like conda-lock or pixi to create a lockfile for the build environment

Run:

mamba env update --file environment.yml --prefix .venv
source activate .venv # or just `activate .venv` on windows

Configure the Widgets Site#

build a jupyter_lite_config.json:

{
  "PyodideLockAddon": {
    "enabled": true,
    "constraints": ["traitlets ==5.14.3"],
    "specs": ["ipywidgets ==8.1.5"],
    "extra_preload_packages": ["ipywidgets"],
    "bootstrap_wheels": [
      "https://files.pythonhosted.org/packages/py3/m/micropip/micropip-0.9.0-py3-none-any.whl"
    ]
  },
  "PyodideLockOfflineAddon": {
    "enabled": true
  }
}

note the tight ipywidgets pin, ensuring compatibility with the build environment
while not required, the constraints option allows for controlling transient dependencies
- this feature requires micropip >=0.9.0, which is only compatible with pyodide >=0.27

Build the Site with Widgets#

build a jupyter_lite_config.json:
```
jupyter lite build
```

Check Widgets Works Offline#

disconnect from the internet ✈️
- this step is optional, but is the most reliable way to validate a reproducible site

start a simple, local development server

cd _output
python -m http.server -b 127.0.0.1

visit the site at http://127.0.0.1:8000/
make a new Notebook
- see that ipywidgets can be imported, and widgets work:
```
import ipywidgets
ipywidgets.FloatSlider()
```

Motivation#

By default, a pyodide distribution provides a precise set of hundreds of package versions known to work together in the browser, described in its pyodide-lock.json.
Among these packages is micropip, which gives site users the ability to install packages not included in pyodide-lock.json. These may be served along with an HTML page, downloaded from PyPI, or anywhere on the internet. jupyterlite-pyodide-kernel uses this capability to install itself, and its dependencies.
- At run time, piplite provides a micropip-based shim for the IPython %pip magic, the most portable approach for interactive package management in Notebook documents.
micropip (and %pip) are powerful for interactive usage, but can cause headaches when upstream versions (or their dependencies) change in ways that either no longer provide the same API expected by the exact versions of pyodide, pyodide-kernel, and JupyterLab extensions in a deployed JupyterLite site.

jupyterlite-pyodide-lock gives content authors tools to manage their effective pyodide distribution, making it easier to build, verify, and maintain predictable, interactive computing environments for future site visitors.

Why Use This?#

in the browser
- fetches pyodide-kernel, its dependencies, and configured packages in parallel while pyodide is starting, skipping micropip.install and its requests to the PyPI API
- doesn’t require %pip install for locked packages and their dependencies
  - notebooks and scripts still need to be well-formed, e.g. import my_package
  - once shipped, package versions loaded in the browser won’t change over time
during a build
- doesn’t require rebuilding a full custom pyodide distribution
  - but will patch an custom deployed pyodide
  - all downloaded wheels can be optionally shipped along with the application
- optionally clamp PyPI packages to a known timestamp to ensure newer packages aren’t found during a future solve
- supports multiple sources of custom wheels and dependencies

Feature Comparison#

A number of approaches are available for getting reproducible JupyterLite runtime python environments, either with jupyterlite-pyodide-kernel or other kernels. Choosing one requires some trades of simplicity, reproducibility, flexibility, and performance.

⏱️ Note

Each tool is evolving, so the tables below should be verified against the different tools when making a decision.

A visitor to a JupyterLite site's needs may be the top priority...

feature	`jupyterlite-pyodide-lock`	`piplite`	jupyterlite-xeus	micropip
needs separate `install` and `import`	no (for locked packages)	yes (`%pip`)	no	no
allows install by PyPI name	yes	yes	yes	yes
allows install from URL	yes	yes	no	yes
blocks interaction per package	run cell	run cell	start kernel	run cell
caches in the browser	per package	per package	whole environment	per package

An author of a JupyterLite site may have additional needs...

feature	`jupyterlite-pyodide-lock`	`piplite`	jupyterlite-xeus	pyodide-build
requires “heavy” build dependencies	real browser (and/or `selenium`)	no	minimal, see repo	many, see repo
ships local wheels	yes	yes	maybe?	yes
ships noarch PyPI wheels	yes	yes	yes	yes
ships pyodide emscripten wheels	yes	yes	no	yes
ships arbitrary pyodide zip C libs	no	yes	no	yes
locks multiple versions of same package	no	yes	no	no
optionally clamp to a timestamp	yes	no	no	no